The objectives of the Registry of Experimental Cancers are: 1) The storage and retrieval of pathologic material and data on cancers and other lesions of laboratory animals (primarily rodents) and 2) the use of such information for research and educational purposes. The Registry has acquired a total of 1809 (474 since the 1978 report) single or group accessions from investigators outside the NCI. Approximately 50,000 (12,000 since the 1978 report) records have been prepared for coding and coded. Forty-eight investigators have come to the Registry for study and consultation on single or multiple visits. Three foreign investigators were guests at the Registry for 2 days, 3 days and 6 weeks respectively.